This application relates to a method and apparatus for checking to ensure an acceptable wall thickness in a hollow airfoil, such as are utilized in gas turbine engines.
Gas turbine engines are known, and include a plurality of sections mounted in series. A fan typically delivers air downstream to a compressor, and the compressor compresses the air. The compressed air is delivered into a combustor section, where it is mixed with fuel and combusted. Products of the combustion move downstream over turbine rotors, and drive the turbine rotors to rotate.
The turbine rotors typically include a plurality of removable blades. The turbine rotors are separated by static vanes. The blades and vanes have an airfoil shape, and become quite hot from the products of combustion. To address the high temperatures, the airfoils are generally hollow with internal air cooling channels. Air is circulated through these air cooling channels.
In a typical method of forming the hollow airfoils, a plurality of lost core mold cores are placed within a mold. Molten metal then flows into the mold, and surrounds the mold cores. The mold cores are then leached away, leaving spaces where the mold cores were initially placed. From this, the metal forms the airfoil, and the spaces where the mold cores were received, form the air cooling channels.
The shape and design of the airfoils and the cooling channels has become more and more complex, and it has become difficult to check the wall thickness between the cooling channel and an outer surface of the airfoil. It is necessary to maintain the wall thickness within a tolerance range. It is undesirable to have the wall thickness be too thin, or too thick.
However, to date, it has been somewhat difficult to check the wall thickness in an airfoil, and in particular at certain locations within the airfoil.